Constant velocity joints connecting shafts to drive units are common components in automotive vehicles. The drive unit typically has an output shaft or an input shaft for receiving the joint. Typically, the drive unit is an axle box, transfer case, transmission, power take-off unit or other torque device, all of which are common components in automotive vehicles. Typically, one or two joints are assembled to the shaft to form a propeller or drive shaft assembly. The propeller shaft assembly may be connected, for instance, at one end to the output shaft of a transmission and, at the other end, to the input shaft of a differential. The shaft may be solid or tubular with ends adapted to attach the shaft to an inner race of the joint. An outer race of the constant velocity joint may be connected to the drive unit. The inner race of the joint is typically press fit, splined, or pinned to the shaft, making the outer race of the joint available to be bolted or press fit to a hub connector, flange or stubshaft of the particular drive unit. At the other end of the propeller shaft, a similar connection is made to a second drive unit when connecting the shaft between the two drive units.
Motor vehicles may use propeller or drive shafts to transfer torque via the constant velocity joint from the one input unit to an output unit, for example, from a front drive unit to a rear axle differential such as in rear wheel and all wheel drive vehicles. Propeller shafts are also used to transfer torque and rotational movement to the front axle differential in four-wheel drive vehicles. In particular, two-piece propeller shafts connected by an intermediate joint are commonly used when larger distances exist between the front drive unit and the rear axle of the vehicle. Similarly, inboard and outboard axle drives are commonly used in motor vehicles to transfer torque from a differential to the wheels. The torque transfer is achieved by using a propeller shaft assembly consisting of one or two joints assembled to an interconnecting shaft in the manner indicated above.
Joint types that may be used include Cardan, Hooke or Rzeppa type universal joints. Typically, Rzeppa type constant velocity joints are employed where transmission of a constant velocity rotary or homokinetic motion is desired or required. Constant velocity joints include tripod joint, double offset joint, and cross groove designs having plunging or fixed motion capabilities. The tripod type constant velocity joint uses rollers or trunnions as torque transmitting members and the other constant velocity joint types use balls as torque transmitting members. These types of joints assembled to an interconnecting shaft are applied in inboard axle and outboard axle drives for front wheel drive vehicles and on the propeller shafts found in rear wheel drive, all-wheel-drive, and four-wheel drive vehicles allowing for angular articulation or axial motion. As between the fixed and plunging types of constant velocity joints, the plunging joint typically experience more noise, vibration and harshness (“NVH”) issues due to sliding forces as well as clunking noise due to joint tolerances.
The torque transfer capability of a cross-track constant velocity joint is also influenced by its moment of inertia, which is primarily a function of the maximum radii of the constant velocity joint's parts, rather than their mass. Thus, it would be desirable to have an improved cross-track constant velocity joint that benefits from the torque transfer to radius relationship to reduce the mass of the assembly. Moreover, a cross-track constant velocity joint that provides a reduced package size for a particular application would also be of benefit. Also, a cross-track constant velocity joint with optimized ratios would provide additional benefits, such as weight reduction, package size control, reduced part envelope and/or part runout, improved vibration deadening, increased strength per package size, and increased torque transfer capability per unit weight.